DARPA’s Phoenix: Making The Most of Space Junk.

by David Klemke on October 25, 2011

Debris in orbit are becoming one of the greatest challenges that we face as we become a space fairing species. You see by the simple fact that something is in orbit means that it has an incredible amount of potential energy, zipping around the earth at Mach 25 ready to wreck anything that might cross its path. Thankfully there’s quite a lot of empty space up there and we’re really good at tracking the larger bits so it’s usually not much of an issue. However as time goes by and more things are launched into orbit this problem isn’t going to get any better, so we need to start thinking of a solution.

Problem is that recovery of space junk is an inherently costly exercise with little to no benefits to be had. A mission to recover a non-responsive satellite or other spacecraft is almost as complex as the mission that launched said object in the first place, even more so if you include humans in the equation. Additionally you can’t send up a single mission to recover multiple other missions as typically satellites are on very different orbits, done so that they won’t collide with each other (although that has happened before). Changing orbits, known as a plane change, is extremely expensive energy wise and as such most craft aren’t capable of changing more than a couple degrees before their entire fuel supply is exhausted. The simple solution is to deorbit any spacecraft after its useful life but unfortunately that’s not the current norm and there’s no laws governing that practice yet.

It’s even worse for geostationary satellites as in that particular orbit things don’t tend to naturally deorbit over time. Instead anything in a geostationary orbit is pretty much going to be there forever unless some outside force acts on them. Geostationary orbits are also particularly valuable due to their advantageous properties for things like communication and location so the problem of space debris up there is of a much bigger concern. Thankfully most geostationary satellites have the decency to move themselves into a graveyard orbit (one just outside geostationary which will eventually see them flung from earth orbit) but this method isn’t guaranteed. Mass that’s already in orbit is incredibly valuable however and DARPA has been working on a potential solution to debris in geostationary orbit.

The DARPA Phoenix program is an interesting idea, in essence a in orbit salvager that cannibalizes other satellites’ parts in order to create new “satlets”. These new satlets won’t be anywhere near as capable as their now defunct donors were but they do have the potential to breathe a whole lot of life back into the hardware that’s just sitting there idle otherwise. Compared to a regular geosynchronous mission something like Phoenix would be quite cheap since a good chunk of the mass is already up in orbit. Such a mission can really only be done in geostationary orbit since all the satellites are in the same plane and the energy required to move between them is minimal. That is our most valuable orbit however so such a mission could prove to be quite fruitful.

Dealing with the ever growing amount of space debris that we have orbiting us is a challenge that we’ve still yet to answer. Programs like DARPA’s Phoenix though are the kinds of projects we’ll need to both reduce the amount of orbital junk we have as well as making the most out of the stuff we’ve already put up there. I’m really keen to see how the Phoenix project goes as it’d would be quite a step forward for on orbit maintenance and construction as well as being just plain awesome.